<!doctype html>
<html>
<head>
    <meta charset="UTF-8">
    <title>顶部广告展开收起</title>
    <style>
        body, div, img, span {
            margin: 0;
            padding: 0;
        }

        #content {
            width: 960px;
            height: 1000px;
            background: #ccc;
            margin: 0 auto;
        }

        #ad {
            width: 960px;
            margin: 0 auto;
            display: none;
            position: relative;
            overflow: hidden;
        }

        #close {
            position: absolute;
            width: 20px;
            height: 20px;
            text-align: center;
            line-height: 20px;
            background: #CF3;
            top: 0;
            right: 0;
            display: none;
            cursor: pointer;
        }
    </style>
</head>
<body>
<div id="ad">
    <img id="adcon" src="ad.png" width="960" height="386"/>
    <img id="adcur" src="cur.png" width="960" height="68"/>
    <span id="close">X</span>
</div>
<div id="content"><img src="数字商品-10-23.jpg"/></div>
<script>
    //全局变量
    /*var oAd     = document.getElementById('ad');
    var oAdcon  = document.getElementById('adcon');
    var oAdcur  = document.getElementById('adcur');
    var oClose  = document.getElementById('close');
    */
    var getId = function (id) {
        return document.getElementById(id);
    }
    var maxH = getId('adcon').height;//最大高度
    var minH = getId('adcur').height;//最小高度
    var step = 5;//移动的距离
    var h = 0;

    /*广告向下展开*/
    function adDown() {
        if (h < maxH) {
            h += step;//向下移动
            setTimeout(adDown, 1);
        } else {
            setTimeout(adUp, 3000); //停留时间自己适当调整 1000 = 1秒
        }
        getId('ad').style.display = "block";
        getId('ad').style.height = h + "px";
    }

    /*广告向上收起*/
    function adUp() {
        getId('ad').style.height = h + "px";

        if (h > minH) {
            h -= step;
            setTimeout(adUp, 1);
        } else {
            getId('adcon').style.display = "none";
            getId('close').style.display = "block";
        }
    }

    getId('close').onclick = function () {
        getId('ad').style.display = "none";
    }
    setTimeout(adDown, 3000);
</script>
</body>
</html>
